refactor: 💡 Remove route-action usage for managed-groups (#2168)

* refactor: 💡 Remove route-action usage for managed-groups

✅ Closes: https://hashicorp.atlassian.net/browse/ICU-12619

ui/admin/app/components/auth-methods/auth-method/managed-groups/managed-group/actions/index.hbs

@@ -12,7 +12,7 @@
     <dropdown.button
       @style='danger'
       @disabled={{@model.canSave}}
-      {{on 'click' (route-action 'deleteManagedGroup' @model)}}
+      {{on 'click' (fn @delete @model)}}
     >
       {{t 'resources.managed-group.actions.delete'}}
     </dropdown.button>